Australia's Heart Foundation foresees guidelines on sitting less in addition to current physical activity suggestions. (CBC)

Spending more time sitting in front of the TV increases the risk of an early death from heart disease, regardless of your weight, researchers in Australia suggest.

The team followed 3,846 men and 4,954 women, average age 50, who did not have a history of cardiovascular disease.

For about seven years, researchers monitored blood pressure, cholesterol levels and TV habits.

Each hour spent sitting in front of the TV per day raised a person's risk of death from cardiovascular disease by 18 per cent and the risk of dying for all causes by 11 per cent, David Dunstan of the Baker Heart and Diabetes Institute in Victoria and his colleagues reported in Monday's online issue of the journal Circulation, published by the American Heart Association.

Body's regulation disrupted

"What this study provides is the first compelling evidence linking television viewing to an increased risk of early death," said Dunstan.

Researchers found the increased risk of death from cardiovascular disease in those watching four or more hours of television per day compared with less than two hours per day after taking traditional risk factors such as smoking, blood pressure, cholesterol and diet into account, as well as leisure-time exercise and waist circumference.

During the course of the study, 284 people died, including 87 from heart disease and 125 from cancer. Television viewing was a significant predictor of cardiovascular but not non-cardiovascular mortality, the researchers said.

Watching TV involves "prolonged sitting, because that's the default position, and from that there's an absence of muscle movement," said Dunstan.

"We know from extensive evidence that muscle contractions are so important for many of the body's regulatory processes, such as breaking down and using glucose, so that loss of muscle movement for prolonged periods may result in a disruption to the body's regulatory processes."

Move more often

"Although continued emphasis on current public health guidelines on the importance of moderate- to vigorous-intensity exercise should remain, our findings suggest that reducing time spent watching television (and possibly other prolonged sedentary behaviors) may also be of benefit in preventing [cardiovascular disease] and premature death," the study's authors concluded.

Dunstan suggested that people keep in mind to "move more, more often."

Television-watching is the most common sedentary activity carried out in the home, according to previous studies in the U.S., Australia and the United Kingdom.

The findings highlight an important new field of study, said Trevor Shilton from Australia's Heart Foundation.

"I can foresee a time where we will have, in addition to our guidelines, a defined 30 minutes of physical activity, also guidelines about moving more and standing more throughout the day," said Shilton.

"And about sitting less, standing up every 20 minutes, going for a walk at work, having rules around television and computer times for our kids."

The television viewing assessed in the study was based on self-reports, which may have led to some misclassification, the researchers acknowledged.

The study was funded by the National Health and Medical Research Council and the Australian Institute of Health and Welfare, and several pharmaceutical and device manufacturers.

With files from the Australian Broadcasting Corp.